Breaking with Cocker, The Grease Band continued to mine a powerful vein of gritty blues, earning them a live reputation that has rarely been equalled. Around this time Henry landed himself an audition for a gig with ex-Beatle Paul McCartney resulting in the formation of the first—and many say the best—incarnation of Wings which included the line up of Denny Seiwell, Denny Laine, and Linda McCartney. During one Wings session at Abbey Road when Pink Floyd were recording in an adjacent studio, Henry made a spoken contribution to the classic Dark Side of the Moon.

Following a gut-level instinct for rock has always seen McCullough in well respected company, playing guitar and gigging with Roy Harper, Marianne Faithfull, Ronnie Lane, Donovan, Frankie Miller, Eric Burdon, Viola Wills, Spooky Tooth . . ..